Pleated filter panel elements are widely used in automotive as well as residential and commercial building HVAC applications, among others. Pleated filter elements are typically produced by corrugating or pleating one or more flat sheets of filter media, such as filter paper and then securing the pleats sheets into a periphery seal member. Pleating the filter element is advantageous as it increases the effective filter surface area for a given dimensional size of filter. The presence of pleats in the filter element also provides additional structural strength to resist forces such as those applied to the filter element by a fluid stream passing through the pleated filter element.
One typical application for pleated filter panel elements is in filtering an air stream, such as an intake combustion air stream to an internal combustion engine. Additional common applications for pleated air filter elements include use in motor vehicle cabin air filters as well as heating/cooling system air filtering for commercial and residential applications. In automotive combustion air filtering applications, such filtering elements are often installed into a housing having two halves that may be separated so as to access the housing interior and replace the filter element when necessary. The pleated filter panel element often includes a resilient seal member secured to periphery edges of the filter element. The seal member is often sized and shaped to be received into and sealably engage with a support ledge provided in the filter housing, thereby providing a seal between the filter element and the housing to prevent the air stream from bypassing the filter in any open space between the filter housing and the filter element. In applications where a filter housing is not utilized, a filter support member such as a filter support frame may be provided to receive the filter element, for example when an air filter is installed in an air duct for a building HVAC application.
When a pleated filter element is utilized in automotive engine air induction system applications, the filter may be required to be installed into a specified orientation (oriented with the pleat folds aligned in a specified direction). In certain cases the dimensions of a rectangular panel pleated air filter element may permit the pleated filter element to be physically installed into the filter housing or support frame even when filter is incorrectly oriented (for example, with the filter pleat folds rotated 90 degrees out of the correct installation orientation). In applications where a specified orientation of the filter pleats is important, the requirement for a specific filter orientation may not always be readily apparent to the person installing the filter, especially when the filter element dimensionally approximates a square. In some cases the shape and dimensions of the filter may be such that the filter can be forced to install into the housing or support frame an incorrect orientation. One drawback of an incorrectly oriented filter element is that it may not seal correctly into the filter housing, thereby allowing an unfiltered portion of the fluid stream to bypass the filter and carry contaminants into the clean side of the filter.
It is known in the current art to indicate the filter orientation for installation by providing special orientation features directly on the air filter element itself that mate with complimentary features in the support frame or filter housing. Conventional types of orientation features include special orientation features on the filter such as notches or tabs that are sized and configured to mate with corresponding complimentary features in the support frame or housing. These known approaches to enforcing filter orientation during filter installation are not always effective as they rely upon orientation features formed into the gasket of the filter element, which is typically a soft, pliable and easily deformed material. Necessarily, the filter gasket material is soft by design in order to provide a seal between the filter element and the support frame or filter housing. Filter orientation features formed into the gasket material of the filter results in a unreliable orientation feature because the end user can physically overcome the orientation features and cause the filter to install into an incorrectly orientated position. An incorrectly oriented filter may not even be apparent to the installer due to the weakness of orientation features that are built using the pliable filter gasket or seal material to guide orientation.
Also known in the art are filter elements in which the pleated filter media core is replaceably installed onto a reusable support rack member. The support rack member includes a plurality of comb-like spacer elements (typically one for every filter pleat) that configured and positioned to be received between the pleats of the pleated media and thereby provide support to the pleated media.
U.S. Pat. No. 5,840,094 discloses a filter assembly including first and second frame members, a filter element, and separate comb-like spacers for retaining the filter pleats in an open spaced manner.
U.S. Pat. No. 6,033,453 discloses a reusable frame support rack for supporting and retaining an outstretched, replaceable pleated media filter core. The frame includes a pair of longitudinal angles extending between a pair of transverse angles which carry a flat expanded metal support or reinforcement system.
Additionally, a filter element that is installed in an incorrect orientation has other undesirable effects, particularly when utilized in an automotive air induction system air filter. Specifically, an automotive engine air induction system typically includes a flow sensor known as a Mass Air Flow Sensor (MAF). The MAF is typically located after the clean side of the filter and before the engine intake air manifold. The Mass Air Flow Sensor (MAF) provides a primary measurement of the flow rate of air into the engine through the air induction system. The measured air flow rate is utilized and relied upon by the Engine Control Unit (ECU) computer to accomplish regulation of the quantity of fuel injected into cylinders of the engine. An incorrect orientation of the pleats of a pleated air filter alters the air flow pattern seen by the MAF sensor. This altered air flow pattern may result in an error in the air flow measurement reported by the MAF sensor to the ECU, thereby affecting the ratio of fuel to air delivered to the engine and undesirably resulting in non-optimum engine operating performance and increased emissions.
Therefore, a need remains for a device to enforce correct orientation of a filter element during installation and to resist installation of an incorrectly oriented filter element. Additionally a need also remains for a device that reliably indicates to a technician when a filter element is incorrectly oriented during installation so that corrective action can be taken.